Huge increase in UT compile time

[Dhananjay]

Another observation:
wc -l test.dep (for "-deps=test.dep ... -unittest -main" command):
Linux 2.076.1: 41389
Linux 2.069.1: 144

Making small changes to 2.069.1 runtimes (I had run with a 
different program by mistake. The measurement is still of the 
same order)

On Wednesday, 11 October 2017 at 06:25:19 UTC, Dhananjay wrote:
> Hello,
>
> I am upgrading to DMD 2.076.1 from DMD 2.069.2 (similar results 
> on 2.075.1), and seeing a huge increase in unittest compilation 
> time when the -deps parameter is also passed to dmd. This is on 
> both OSX and linux. What can be the cause of this?
>
> Sample program:
>
>     import std.stdio: writeln;
>
>     unittest { writeln("TestUT"); }
>
>     version (unittest) {}
>     else
>     {
>         void main()
>         {
>             writeln("TestMain");
>         }
>     }
>
> Observations:
>
> Command: time dmd -deps=test.dep -c -o- test.d -de -w -m64 
> -color -g -debug -gs -unittest -main
> Linux runtime: user 0m28.192s    << Note the increase
> OSX runtime: user 0m48.508s     <<
     Linux 2.069.1 runtime: user 0m0.045s <edited>
>
> Command: time dmd -c -o- test.d -de -w -m64 -color -g -debug 
> -gs -unittest -main
> Linux runtime: user 0m0.064s
> OSX runtime: user 0m0.090s
    Linux 2.069.1 runtime: user 0m0.053s <edited>
>
> Command: time dmd -deps=test.dep -c -o- test.d -de -w -m64 
> -color -g -debug -gs
> Linux runtime: user 0m0.584s
> OSX runtime: user 0m0.882s
   Linux 2.069.1 runtime: user 0m0.035s  <edited>
>
> Command: time dmd -c -o- test.d -de -w -m64 -color -g -debug -gs
> Linux runtime: user 0m0.048s
> OSX runtime: user 0m0.074s
   Linux 2.069.1 runtime: user 0m0.036s   <edited>
>
> Environment:
> OSX: El Capitan 10.11.6
> Linux with DMD 2.076.1: Gentoo 4.9.34
> Linux with DMD 2.069.1: Centos 7